Abstract
BackgroundNumerous laboratory and fewer field-based studies have found that ixodid ticks develop more quickly and survive better at temperatures between 18 °C and 26 °C and relative humidity (RH) between 75 and 94%. Ixodes anatis Chilton, 1904, is an endophilic, nidicolous species endemic to North Island brown kiwi (Apteryx mantelli) (NIBK) and the tokoeka (Apteryx australis), and little is known about the environmental conditions required for its development. The aims of this study were to determine and compare the conditions of temperature and RH that ensure the best survival of the kiwi tick and the shortest interstadial periods, in laboratory conditions and outdoors inside artificial kiwi burrows.MethodsFree-walking engorged ticks were collected off wild kiwi hosts and placed in the laboratory under various fixed temperature and humidity regimes. In addition, sets of the collected ticks at different developmental stages were placed in artificial kiwi burrows. In both settings, we recorded the times taken for the ticks to moult to the next stage.ResultsLarvae and nymphs both showed optimum development at between 10 °C and 20 °C, which is lower than the optimum temperature for development in many other species of ixodid ticks. However, larvae moulted quicker and survived better when saturation deficits were < 1–2 mmHg (RH > 94%); in comparison, the optimum saturation deficits for nymph development were 1–10 mmHg.ConclusionsOur results suggest that the kiwi tick has adapted to the stable, but relatively cool and humid conditions in kiwi burrows, reflecting the evolutionary consequences of its association with the kiwi.Graphical
Highlights
The amount of time that each life-cycle stage of ticks takes to complete is determined by interactions between temperature and moisture in the off-host habitat [1,2,3]
Ixodes anatis Chilton, 1904, is a host-specific ixodid tick found on apterygid birds, which include the North Island brown kiwi (Apteryx mantelli) (NIBK) and the tokoeka (Apteryx australis); as such, this tick is endemic to New Zealand [17, 18]
In the first, engorged larvae, nymphs and adults were incubated under laboratory conditions; in the second, engorged ticks were maintained in artificial kiwi burrows in a forested area close to the laboratory (40.3709°S, 175.6303°E; Fig. 1)
Summary
The amount of time that each life-cycle stage of ticks takes to complete is determined by interactions between temperature and moisture (relative humidity [RH]) in the off-host habitat [1,2,3]. Ixodes anatis Chilton, 1904, is a host-specific ixodid tick found on apterygid birds, which include the North Island brown kiwi (Apteryx mantelli) (NIBK) and the tokoeka (Apteryx australis); as such, this tick is endemic to New Zealand [17, 18]. It is an endophilic, nidicolous species which has only been recovered either from the body of the hosts or within their burrows. Ixodes anatis Chilton, 1904, is an endophilic, nidicolous species endemic to North Island brown kiwi (Apteryx mantelli) (NIBK) and the tokoeka (Apteryx australis), and little is known about the environmental conditions required for its development. The aims of this study were to determine and compare the conditions of temperature and RH that ensure the best survival of the kiwi tick and the shortest interstadial periods, in laboratory conditions and outdoors inside artificial kiwi burrows
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